Polyamide acid composition and method of preparation

ABSTRACT

A POLYAMIDE-ACID IS PREPARED BY REACTING A DIANHYDRIDE WITH A DIAMINE FORMED FROM THE REACTION OF A DIEPOXIDE COMPOUND AND A DIAMINE. THE RESULTANT POLYAMIDE-ACID IS THEN CONVERTED TO A POLYIMIDE BY HEATING. THE POLYIMIDE COMPOUND IS USEFUL FOR ELECTRICAL INSULATING PURPOSES, ESPECIALLY IN THE FORM OF COATINS ON ELECTRICAL CONDUCTORS.

United States Patent "ic 3,619,632

Patented July 25, 1972 ized by a formula as shown above wherein m ranges from 3,679,632 about 16 to about 27. POLY M E C COMPOSITION AND Other epoxy compounds which may be used are di- METHOD OF PREPARATION epoxides of cyclo-aliphatic type, examples of which are Ralph G. Flowers Pittsfield and Thomas L. Sherer Richmond, Mass; g to General Electric i 5 dlcyclodlepoxycarboxylates, e.g., 3,4 epoxy cyclohexyl pally methyl 3,4 epoxy-cyclohexanecarboxylate, and 3,4- No Drawing. Continuation-impart of application Ser. No. ePOXY 6 y Y eXy1methyl-3,4-epoxy-6-methy1- 641,131, May 25, 1967. This application Dec. 29, 1969, cyclohexanecarboxylate.

Ser. No. 888,852 Another example of a cyclo-aliphatic diepoxide is a Int. Cl. C08g 20/32 10 cyclodiepoxydicarboxylate such as the diglycidyl ester US. Cl. 260-47 CP 4 Claims. of hexahydrophthalic acid, which has the following formula:

ABSTRACT OF THE DISCLOSURE /O\ o 0 A polyamide-acid is prepared by reacting a dianhydride mo CH-ii0CH Cfi- CH with a diamine formed from the reaction of a diepoxide CH CH OH compound and a diamine. The resultant polyamide-acid H o a a is then converted to a polyimide by heating. The poly- I a 0 imide compound is useful for electrical insulating purhi h d th Poses, especially in the form of coatings on electrical The dlamme w c 1s reacte W1 6 epoxy conductors, pound in accordance with the invention has the formula:

(I) H N--RNH The Present application is a eontinuetion'in'pait of where R is a divalent organic radical selected from sub- Peiidiiig application 641,131 filed y 1967, 25 stituted and unsubstituted aliphatic, cycle-aliphatic, BOW aharlderied, and assigned to the same essignee as heterocyclic, and aromatic groups, and combinations of the Present epplieatiorlsuch groups such as aliphatic-aromatic groups, the two It is an Object of the invention to Provide novel P amino groups being attached to different carbon atoms. imide compounds useful for electrical insulating pur- Dial-nines f lj h ti ti type may be obtained P and especially in the i of films matings on by reacting (1) at least one dibasic acid having the electrical conductors, and to provide novel intermediate formula; ggnullffltlons useful in the preparation of such com It is another object of the invention to provide polywhere R' is an unsaturated or saturated aliphatic group imide compounds of the above YP having g fleXibiI- containing from about 1 to 40 carbon atoms with (2) ity, adherence, thermal stability, toughness and electrical n aromatic diamine of the type shown in Formula I properties, and which are easily and economically made bove, from a Wide Variety Of readily obtainable materials. Among the aliphatic dibasic acids which may be utilized It is a Particular Object of the invention to Provide are oxalic, malonic, succinic, glutaric, adipic, pimelie polyimide compounds of the above yp Which are readsuberic, azelaic, sebacic and dodecanedioic acids, as well l moidehle at temperatures generally lower than as unsaturated acids falling within the above formula inq for known yp of polyimide pounds. eluding maleic and fumaric acids, among others.

Briefly, the present invention relates to novel diamine A dibasic acid having a chain thirty-six carbons long diepoxide adducts and to novel polyamide-acids and p vis Emery Industries, Inc. 37134: Dimer Acid. Others will imides prepared therefrom. The diamine diepoxide ad- 09cmt th skilledinthe art.

duet is P P y reacting a diepoxide compound with Among the diamines which may be used are those a i i e, e latter being present in one e i excess listed in Edwards Pat. 3,179,614 and elsewhere, includ- The diepoxide compound y comprise a polyether ing benzidine, 4,4'-diaminodiphenyl ether, 3,3' dimederivative of a Polyhydric Organic compound, e p ythoxy-4,4'-diaminodiphenyl methane, meta-phenylenedihydric alcohol or phenols containing at least two amine, parwphenylenediamine, d h

Pheiioiic y y groups, said derivatives containing 2 [In preparing the polyamide-diamine, dibasic acid is reePOXY groups Such {omPounds and methods of making acted with diamine, which latter is about one mole in themfire Well imown the They may h Prepared by excess, in a cresol solution to form about a 50% by eiteetlng reaction between a Polyhydfle Phen01 such weight solution. Typically, the reactant mixture is reas hydroquinone, resorcinol, and condensation products fl d with stirring f about 11/ to 7 hours i di of phenol with a ketone, e.g., bis-(4-hydroxyphenyl)-2,2- lation of water f the j t P and (2) eplhalogenohydrin, epichlorohy The polyamide-diamine thus obtained may be exdrln. Such epoxy compounds are disclosed for example in Cass 2,691,007 and other patents therein mentioned. pressed by the formula: For example, the reaction of epichlorohydrin with bis-(4- (In) O 0 hydroxyphenyl)-2,2-propane produces an epoxy resin HeN-RNi JR'iiNR-NH, having the following formula:

F E 1 E CHzCHCHzO --o-oni-on-om-o-- ---o-crhcn-- oni L is. is l. l 0

where m 18 the mimber of repeating umts and has an where R is as defined above, R is a saturated or unsatuaverage value varying from about zero to about 27. A

table of data on various epoxy resins of the above type rated aliphatic hydrocarbon containing from about produced by Shell Chemical Corp., under the name of 1 to 40 carbon atoms! e about to Epon resins are shown in Table I in the aforementioned Examples of other diamines which y be p y Cass patent. Epon resin 1009 shown therein is characterare ethylenediamine, propylene diamine, 1,4-cyclohexane bis-(methylamine), m-xylylene diamine and 3,3'-diamino- 1v dipl-opylamine v t .v

The reaction between the diamine and the epoxide compound may be carried out by dissolving the diamine in a; suitable solvent such as cresol using heat, e.g., about 80 C.-100 (3., the amount of solvent being sufiicient to providea 20% by weight solution of the final polymer. The amountvof the diamine used is about 1 mole in excess. The diepoxide compound is then added to the diamine" solution with stirring, and after all the diepoxide compoundis dissolved, the solution is heated for a period of time sufficient to eifect reaction between the diepoxide compound and the diamine, e.g., one hour at 80 C. or

'Where the cyclodiepoxydicarboxylate mentioned above isused, R" comprises a cyclo-dihydroxy-dicarboxylate having the following formula:

An example of a specific adduct of this type obtained by the reaction of the diglycidyl ether of bisphenol A and p,p-methylene dianiline has the following formula:

1;: "a CH3 1 I mmQ-om-Q-nnomomemo-@4 oonzononmn-om--Nm on (in, bu

minutes at 100 C. Themiirture is'then cooled to a temperature in the range of about room temperature to A different specific adduct obtained by the reaction of hexamethylene diamine and diglycidyl ether of bisphenol A has the following formula:

about 50' CLThe product of this reaction is a diamine diepoxide adduct having the general formula:

(IV) H NR-NH-R"NH-} RNH where [R is as defined above, R is an aromatic-containing or cyclo-aliphatic group having 'at least two OH groups beta to the NH groups, and x varies from about 1 to 3. By beta is meant that the OH group is attached to a carbon atom which is separated from the corresponding NH group by one carbon atom. Examples of aromatic-containing groups which R" may comprise are the where m is the number of repeating units and from about 0 to about 27.

Examples of a cycle-aliphatic group which R may comprise based on the dicyclodiepoxycarboxylates mentioned above are dicyclo-dihydroxy-carboxylates such 'as the following:

varies Still another adduct obtained by the reaction of p,p"- methylene dianiline and the diglycidyl ester of hexahydrophthalic acid has the following formula:

CH: A diamine diepoxide adduct thus obtained is then reacted in. substantially equimolar amounts with a dianhydride having the formula:

' wherein R is a tetravalent organic radical selected from substituted and unsubstituted aliphatic, cyclo-aliphatic, heterocyclic, and aromatic groups, and combinations of such groups such as alkylene-aromatic hydrocarbon groups. Among the dianhydrides useful in this connection are bis(3,4dicarboxyphenyl) methane dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 3,4,4',4'-benzophenone tetracarboxylic dianhydride, etc.

Other dianhydrides which may be employed are Nadic dianhydride, benzalazine dianhydride, cyclopentane dianhydride, ethylene-bis(trimellitate) dianhydride, and others.

The reaction between the dianhydride and the diamine epoxy adduct may be carried out by adding dry powdered dianhydride to the thus formed diamine diepoxide adduct in about equimolar amounts with stirring. After about 30 minutes the polyamide-acid has been formed. This polymer may either be converted directly to the polyimide by heating the solution to 80-100 C. or applied to the article to be coated thereby, and the coating is cured in situ preferably for about 10-20 minutes at about 220 C., or in'suitable cases for shorter periods at temperatures up to 300 C. or higher.

Alternatively, for molding or laminating purposes, the diepoxide compound and the diamine may be formed into a homogeneous mixture without the use of a solvent, and the mixture is heated to produce the reaction as described above. This cooled mixture is then pulverized and thoroughly blended withthe powdered dianhydride, and this mixture is subjected to suitable pressure at a temperature of about 275300 C. to produce a rigid structure.

The product obtained from the reaction between the diamine diepoxide adduct and the dianhydride is a polyamide-acid having the general formula:

where R, R", R and x are as defined above and n is at least two.

When the solution of the latter compound is applied to the article to be coated thereby and then cured at the temperatures mentioned above, the polyamide-acid is converted to a polyimide having the general formula:

where the various constituents are as defined above.

The examples below will illustrate the practice of the invention, it being understood that they are to be taken as exemplary only. In the examples, the amounts of the ingredients are given in parts by weight:

EXAMPLE 1 In this example, a cyclo-aliphatic epoxide compound, 3,4 epoxy-cyclohexylmethyl-3,4-epoxy-cyclohexanecarboxylate, 12.6 parts, was dissolved in 100 parts N-methyl- 2-pyrrolidone, and this was reacted by heating at a temperature of about 100 with 19.8 parts of p,p'methylene dianiline in 100 parts of the same solvent. This mixture was cooled and then added to a solution of 161 parts of benzophenone tetracarboxylic acid dianhydride in 100 parts of the same solvent. The solution of the reaction product thus obtained was cast onto a thin aluminum sheet in the form of a coating, and this was cured at 220 C. for 10 minutes and thereafter at 300 C. for 5 minutes. A tough, flexible, tightly adherent film 1 mil thick was obtained on the aluminum sheet. This film, as well as all those produced in the following examples, had good electrical insulating properties.

6 EXAMPLE 2 Diglycidyl ether of resorcinol, 11.1 parts, was mixed in about 275 parts cresol with 19.8 parts of p,p'-methylene dianiline and 16.1 parts of benzophenone tetracarboxylic acid dianhydride. The solution obtained thereby was cast onto a thin aluminum sheet and cured at 220 C. for 10 minutes followed by 5 minutes at 300 C. Tightly adherent, flexible films up to 4 mils thick were thus obtained on the aluminum sheet.

EXAMPLE 3 A solution of p,p'-methylene dianiline, 19.8 parts, in 260 parts of cresol was prepared by heating to C. Diglycidyl ether of bisphenol A [bis(4-hydroxyphenyl) 2,2-propane], 17.0 parts, was added to the warm cresol solution while stirring. This solution was kept at 80 C. for one hour before cooling to room temperature. Benzophenone tetracarboxylic acid dianhydride, 16.1 parts, was added to the diamine-epoxy complex solution and stirred at 50 C. for 30 minutes. A flexible adherent film was formed by casting this solution on an aluminum sheet and curing at 220 C. for 10 minutes.

EXAMPLE 4 An intermediate compound prepared by reacting 2 parts of p,p-methylene dianiline with P1 part azelaic aicd was dissolved in 260 parts cresol along with 8.5 parts of the diglycidyl ether of Bisphenol A, using 27.5 parts of the intermediate composition. This solution was held at 80 C. for one hour before cooling to about room temperature, and then 8 parts of benzophenone tetracarboxylic acid dianhydride was added with stirring continuing for 30 minutes. This solution was cast on a thin aluminum sheet, and after curing at 220 C. for 15 minutes, excellent films which were both very flexible and very adherent to the aluminum sheet were obtained.

EXAMPLE 5 A very flexible film was prepared from a solution similar to that described in Example 3, except that only 15.6 parts of the benzophenone tetracarboxylic acid dianhydride was used.

EXAMPLE 6 A bisphenol A epoxy with an epoxy equivalent of 0.22 g./ g. (Araldite 6060), was added in an amount of 50 parts to a warm solution of 19.8 parts p,p'-methylene dianiline in 420 parts cresol. This mixture was heated to 80 C. for one hour before cooling to room temperature, at which time 16.1 parts of benzophenone tetracarboxylic acid dianhydride was added with stirring. After 30 minutes this solution was cast on aluminum and cured at 220 C. The aluminum was dissolved off with dilute hydrochloric acid, leaving a very flexible free film 5 mils thick.

EXAMPLE 7 The epoxide compound described in Example 6 in an amount of 25 parts was dissolved in a warm solution of 27.5 parts of the reaction product of 2 parts p,p'-methylene dianiline and 1 part azelaic acid, in 295 parts cresol. This solution was heated to 80 C. for one hour before cooling to room temperature, and there was then added 8.0 parts of benzophenone tetracarboxylic acid dianhydride. This solution was stirred for 30 minutes and then cast on a thin aluminum sheet and cured at 220 C. for 10-20 minutes. Very flexible free films 1 to 8 mils in thickness were obtained after removing the aluminum with hydrochloric acid.

EXAMPLE 8 The epoxide compound described in Example 6 (Araldite 6060), 50 parts, and 19.8 parts of p,p'-methylene dianiline were pulverized together until thoroughly mixed. This mixture was melted and held at 100 C. for 30 minutes. It was then chilled and ground together with 10.9 parts of pyromellitic dianhydride. 40 parts of this dry mxiture was placed in a mold between two layers of glass colth and heated to 290 C. for about 30 minutes at 6,000 lbs. pressure. This provided a very strong and rigid laminate.

EXAMPLE 9 The dry mixture as formed in Example 8 in an amount of 36.5 parts was mixed thoroughly with 36.5 parts silica (silex) and molded at 290 C. and 15,000 lbs. pressure into a very hard and heat resistant disk 80 mils thick.

EXAMPLE 10 EXAMPLE 1 1 A solution was prepared of the epoxy compound and the intermediate diamine compound of Example 10 using 1 part and 2.9 parts of these compounds respectively, and 21 parts of cresol. After heating the solution for one hour at 80 C., there was added thereto 1 part of an aromaticaliphatic dianhydride consisting of 7,7 '-(2butenylene) 'di-2 norbornene-S,6-dicarboxylic anhydride (Araldite x8157/118) and this mixture was stirred for 30 minutes. The resulting solution was cast onto an aluminum sheet and cured at 220 C. for 15 minutes, producing a very adherent flexible film which could be creased without fracture.

EXAMPLE 12 Twelve parts of Epon 1009 and one part of p,p-methylene dianiline were dissolved in 83 parts of cresol at 80 C. and the solution was held at this temperature for 30 minutes. After cooling it to 40 C., 0.8 part of benzophenone dianhydride was added and stirred for 30 minutes. The reaction mixture was then heated to 80-100 C. for another 30 minutes. A flexible glass cloth laminate was prepared by immersing strips of glass tape in the solution, removing and then heating them for 10 minutes in a 200 C. oven, and then pressing them at 10,000 p.s.i. and 175 C.

EXAMPLE 13 The process of Example 12 was repeated, using 12 parts I Epon 1009, 0.8 part hexamethylene diamine and 0.8 part benzophenone dianhydride. A film cast from this solution on a thin aulminum sheet and cured for 20 minutes at 200 C. was very flexible and adherent.

EXAMPLE 14 EXAMPLE 15 The process of Example 12 causing parts Epon 1001, 1.16 parts hexamethylene diamine and 1.6 parts benzophenone dianhydride gave a product from which a very flexible tightly adherent thick film (9 mils thick) was prepared.

8 "EXAMPLE 16 A polymer made from 2 parts oxydianiline, 9' parts Epon 1004 and 1.6 parts benzophenone dianhydride by the method of Example 12 produced very flexible tightly adherent films.

EXAMPLE 17 Flexible films were also made by the process of Example 12 using a reaction mixture of 2 parts p,p'-methylene dianiline, 1.5 parts diglycidyl ester of hexahydrophthalic acid (Araldite CY 183) and 1.6 parts benzophenone dianhydride.

EXAMPLE 18 A solution was prepared of 1.74 parts hexamethylene diamine and 3.0 parts of the diglycidyl ester of hexahydrophthalic acid in 30 parts cresol, and it was heated to C. for 30 minutes. This solution was cooled to 40 C. and 1.6 parts of benzophenone dianhydride were added and stirred for 30 minutes. The solution was then heated to C. over a period of 30 minutes. A flexible adherent film was obtained when this solution was cast on a thin aluminum sheet and cured for 20 minutes at 200 C.

EXAMPLE 19 A solution of 2.3 parts hexamethylene diamine and 4.5 parts diglycidyl ester of hexahydrophthalic acid in 50 parts cresol was prepared and processed in the same manner as in Example 18, and 1.6 parts benzophenone dianhydride were added and the solution processed as in Example 18. Films cast from this solution were also very flexible and adherent.

The compositions provided by the invention may be used for various applications such as electrically insulating coatings for wires and other electrical equipment, adhesives, protective films, and other uses.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention. Accordingly, we wish to have it understood that we intend herein to cover all such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A polyamide-acid consisting essentially of the re-,

curring unit Iii H and aliphatic-aromatic groups; R" is a radical selected from the group consisting of and ii l

C Hz

group consisting of aliphatic, cyclo-aliphatic, aromatic, and aliphatic-aromatic groups; R" is a radical selected from the group consisting of:

-CH9('JCHqO--OCH2CHCHP on on -orm'3omo OCHaCHCHrand OH CH:

where R is a divalent organic radical selected from the group consisting of aliphatic, cyclo-aliphatic, aromatic, and aliphatic-aromatic groups; R" is a radical selected from the group consisting of:

H wrpdomo-Q-oomonom- 5 6 H mmicmo-Q and where m is the number of repeating units, and cyclo-dihydroxy-carboxylates obtained as the reaction product of a carboxyl group-containing cycle-aliphatic diepoxide and a diamine, wherein said R" radical has at least two OH groups, two of which OH groups are beta to the NH groups; and x varies from about l-3; with (2) a dianhydride having the formula III where m is the number of repeating units, and cyclodihydroxy-carboxylates obtained as the reaction product of a carboxyl group-containing cyclo-aliphatic diepoxide and a diamine, wherein said R" radical has at least two OH groups, two of which OH groups are beta to the NH groups; R is a tetravalent organic radical selected from the group consisting of aliphatic, cyclo-aliphatic, aromatic, and alkylene-aromatic hydrocarbon groups; at is in the range of about 1-3; and n is at least 2.

3. A metal having a coating thereon of a polyimide as defined in claim 2.

4. The method of making a polyamide-acid which comprises reacting at from about room temperature to about 80 C. (1) a diamine diepoxide adduct having the general formula where R is a divalent organic radical selected from the where R' is a tetravalent organic radical selected from the group consisting of aliphatic, cyclo-aliphatic, aromatic, and alkylene-aromatic hydrocarbon groups.

References Cited UNITED STATES PATENTS 3,179,614 4/1965 Edwards 26030.2 3,242,213 3/1966 Preston et al. 260-558 3,437,636 4/1969 Angelo 260-47 WILLIAM H. SHORT, Primary Examiner L. L. LEE, Assistant Examiner US. Cl. X.R.

ll7128.4, 132 B, 161 P; 16l197, 227; 26030.2, 33.4 P, 65, 78 TF, 326 N UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 679, 632 Dated July 25, 1972 Inventofls) Ralph G. Blowers and Thomas L. Sherer It is certified that error appears in the above-identified patent. and that said Letters Patent are hereby corrected as shown below:

001. l, formula l the number "3" is left out of the last portion of the formula following the bracket.

l 3 C.. I CH V 001.5, line 5, "3, L, H, -"'should read 3,u, ',u

COl. 6, line 26, "aicd" should be acid Col. 7, line 2, "001th" should be cloth Col. 7, line 19, after "solution", insert was Col. 7, line 66, "causing" should be using In the Claims:

Claim 4, line 24, last portion of the formula, "2" should be Signed and sealed this lst a of May 1973.

(SEAL) Attet'st:

FLETCHER, JR. ROBERT GOTTSCHALK attesting Officer Commissioner of Patents 

